in the PACIFIC  1941 - 1945





 WWII Unrestricted Submarine Warfare
in the Pacific Theater 1941 to 1945


A   B   C   D   E   F   G  H    J   K   L  

M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Note: The majority of terminology below refers primarily to the U.S. Navy and/or to U.S. submarines. Several items, however are specific to both U-boats and the German Kriegsmarine and are so noted.



AA - Anti aircraft

AAF - US Army Air Forces

Abaft - Toward the stern of a boat or a ship.

Abaft the beam - Any direction between the beam and the stern

ABDACOM - American/British/Dutch/Australian Command

Abeam - A position 090° or 270° relative to the ship's heading.

Acey deucy - Sailors version of backgammon

Acoustic Torpedo - A torpedo that dtects its target by means of sound, and uses that sound to steer along its path.

ACR - Anti Circling Run device

Admiralty - A body of law that deals with maritime cases.

Adressbuch - (Kriegsmarine) U-Boat codebook used in diguising ocean chart grid positions in radio transmissions.

Advance - The distance gained in the original course when turning.

Aft - A position to the rear or the rear extremity of a given object.

After Trim - Variable ballast tank used to adjust the a submarine's weight and tilting movement.

Air Banks -Groups of large air bottles located in midship ballast tanks to store high pressure air for charging torpedoes, blowing tanks, and other services.

After Battery Compartment - Main section of the submarine behind the control room; houses battery cells and crew living and dining spaces.

AIB - Allied Intelligence Bureau

Air Gap - The Mid Atlantic region that, until 1943, was not covered by British and/or American ASW aircraft.

Air Manifold - A series of valves through which compressed air at 600 psi can be fed into tanks at reduced pressure.

Alarm! - Emergency dive order on a U-Boat.

Amps a side - A measure of motor speed by means of current consumption on older types of boats.

Amtrac - Amphibious tractor, used to ferry troops in a landing assault ashore

Anchor Watch - Detail of hands standing by as a readiness precaution while the ship is in port.

Angle on the Boat - The angle of the keel from horizontal

Angle on the Bow - The angle between the fore-and-aft axis of the target and the Line of Sight (LOS), measured clockwise from the target's bow to starboard (right) or port (left).

Annunciator - An electro mechanical signaling device for sending orders to the engine room.

AO - Oil tanker

AP - Troop transport ship (non-landing)

APR 1 - Non directional radar detector.

Aphrodite - German device used to confuse radar by reflecting impulses.

Armed Guard - US Navy gun crews serving aboard a merchant ship.

Ash Cans - Depth charges

Astern - A position or location behind the ship.

A Scope - A viewing screen of the surface search radar.

ASDIC - Acronym for the British Anti-Submarine Detection Investigation Committee; the name given to a device housed under the hull of an anti-submarine vessel and used in detecting the presence of submerged submarines.

ASV - Airborne microwave radar (10 and 3 cm)

ASW - Anti-Submarine Warfare.

Athos - Radio detection antenna

Athwartships - Direction 90° relative to the fore and aft reference meaning across the ship.

Awash - Condition whereby the seas are flowing over the surface of an object as in decks awash.

Auxiliary Tanks - Variable ballast tanks located amidships and used to obtain neutral buoyancy and adjust trim; one tank generally segregated for storing fresh water.

Azimuth - The bearing of an object from the observer measured as an angle clockwise from true north.

AVG - American Volunteer Group (Flying Tigers)



Bachstelze - (Kriegsmarine) water stilt - auto-gyro like device towed on a cable behind a U-Boat to improve the field of vision of the "flying lookout".

Backwash - Water thrown aft by the turning of a propeller.

Bali - A radar detection aerial.

Ballast - Heavy weight in the hold of a vessel to maintain proper stability, trim or draft.

Ballast Tanks - Sections of the space between the pressure hull and the outer hull, and saddle tanks within the torpedo rooms; blown dry to provide positive buoyancy when the submarine is surfaced and completely flooded to give neutral buoyancy when submerged.

Banca - Small native outrigger

Barge - A craft used to haul materials. Also a motorboat assigned as transportation for Admirals.

Base Course - A reference course or direction desired to be made good when evasive steering is being carried out.

Battalion - (USMC, US Army) Usually about 400-strong, is comprised of three rifle companies, a combat support company and a headquarters company.

Battery Fresh Water Tanks - Storage tanks for the distilled water used in watering the main storage batteries. 

Bathythermograph - A device to record sea temperature and submarine depth and to show any abrupt temperature change or gradient.

Battle Surface - A surfacing operation during which the submarine is made buoyant by blowing tanks and then held down by the bow and stern planes and motor power until she leaps forward. Boats thus handled come up flat, or nearly flat and suddenly enabling quick deployment of gun crews.

Battle Lights - Dim red lights that furnish sufficient light for personnel during darken ship period.

Bay of Biscay - The Atlantic bay between northern Spain and northwestern France.

BB - Battleship (USN)

BD - Battleship Division (USN)

B-Dienst - (Kriegsmarine) Funkbeobachtungsdienst - German radio monitoring and crytographic intelligence service.

BdU - (Kriegsmarine) Befehlshaber der Unterseeboote - Commander in Chief, U-Boats; referred specifically to Admiral Karl Dönitz, but also in reference to his staff and headquarters.

Beam - Measured dimension of a ship at its widest part.

Bearing - Used to define the direction of an object or a course from a particular point.

Bee - U-Boater nickname for aircraft

Bed Pan Commando - Slang nickname for US Navy Pharmacists Mates

Bell Book - A log containing the entries of the various speed and direction orders sent to the engine room.

Bendix Log - An underwater device for measuring own ship's speed.

Betty - Japanese patrol bomber or torpedo plane.

Bilge - Lower part of the vessel where waste water and seepage collect.

Billet - Allotted sleeping space; A man's position in the ship's organization.

Black gang - Slang for engine room crew.

Blackout - A darkened ship.

Bleed in - To let in a small, controlled amount of air or water.

Bletchley Park - The British Government Code and Cipher School, located in a large country house in Buckinghamshire, north of London England.

Blister - Armored bulge in a warship's side as protection against torpedoes.

Blow Ballast - To force water from tanks into the sea with compressed air.

Bluejacket - A Navy enlisted man below the grade of CPO; a "white hat."

Boatswain - A sailor whose main duties pertain to deck and boat seamanship. Pronounced bosun.

Bogey - Unidentified (pssibly enemy) aircraft

Boiler - Synonym for pigboat, sewer pipe, submarine

Bold - (Kriegsmarine) Device used by U-Boats to confuse ASDIC

Boot - Slang for a US Navy recruit or leggings.

Boot - (Kriegsmarine) A German boat or warship; the commander is a non staff officer, and the second in command is called the First Watch Officer, i.e. on a submarine.

Bootskanone - (Kriegsmarine) The gun on the foredeck of a U-Boat.

Bow - Forward end of a vessel

Bow Buoyancy - An additional ballast tank to provide extra buoyancy forward when surfacing or in an emergency situation.

Bow Caps - small doors on the outside ends of a submarine's torpedo doors.

Bow Planes - The pair of horizontal rudders at the submarine's bow, rigged out on diving to help give initial down angle, then used in coordination with the stern planes to control depth.

Brag Rags - Miniature Japanese flags displayed on the conning tower or flown from the periscope shears of WWII US submarines indicating the number of enemy vessels sunk.

Bridge - A raised platform from which a ship is steered, navigated or conned.

Brig - Prison on a ship or shore base.

Brigade - (USMC, US Army) Consists of approximately 2,500 persons commanded by a colonel. The brigade provides mobility, counter-mobility and survivability, topographic engineering and general engineering support to the largest unit - the corps, and augments various divisions. The brigade may contain combat engineer battalions, separate engineer companies, assault float bridges, and topographic and tactical bridge companies.

Broach - The act of breaking through the surface and rising out of the water, sometimes called porpoising.

Broadside - Firing ship's armament or receiving hostile fire perpendicular to the ship's course.

Brow - A gangplank, ladder or walkway leading from the ship to the pier.

BuOrd - (Bureau of Ordnance) Navy Department responsible for weapons and ordnance.

BuPers - (Bureau of Personnel) Navy Department responsible for personnel (Formerly BuNav)

BuShips - (Bureau of Ships) Navy Department responsible for construction and maintenance of naval ships.

Bulkhead - Traditional nautical term for a wall or partition on a ship.

Bulwarks - A structural extension of a ship's sides above the upper deck.

Bunkers - Storage space for fuel (US) or the exterior fuel tanks on a U-Boat



CA - Heavy Cruiser (USN)

Can - Storage batteries.

CAP - Combat Air Patrol (USN)

Capital Ship - A term used throughout WW II to define the most significant warships in a fleet.

Captain - The officer rank between Rear Admiral and Commander (USN). Also a naval officer commanding a warship.

Casing - A submarine's outer skin of light plating which encloses the ballast tanks and pressure hull.

Cast - US cryptanalysis unit (Cavite, Manila Bay)

Cavitation - The formation of a partial vacuum and resulting air bubbles around rotating propeller blades; the collapse of this vacuum creates propeller noises.

CBI - China-Burma-India; operational area for Allied forces in WW II

CD - Cruiser Division (USN)

Chidori - Japanese anti-submarine vessel; a type of torpedo boat

Chief of the Boat - A petty officer in charge of enlisted personnel; generally one of the most experienced of the enlisted men on board.

Chopline - Change of Operational Control (See MOMP)

Christmas Tree - Panel of red and green lights which denote whether valves and vents are open or closed.

Chutai - Japanese word for "squadron"

CIC - Combat Information Center (USN)

Cigarette Deck - The open, railed platform aft of a US fleet submarine's bridge. Similar to a U-Boat's wintergarten.

CinCLant - Commander in Chief, Atlantic Fleet (USN)

CinCPac - Commander in Chief, Pacific Fleet (USN)

Cipher - A secret letter substitution communication coding system.

CL - Light Cruiser (USN)

Clamp Down - Go over the living space decks with a damp swab.

Class - Vessels of the same type built to a common basic design.

Clinometer - Bridge and engine room instrument that indicates the amount of a ship's roll or degree of list.

CNO - Chief of Naval Operations (USN)

Coaming - Raised framework around deck or bulkhead openings and cockpits of open boats to prevent the entry of water.

CO - Commanding Officer (USN)

COMINCH - Commander in Chief, United States Fleet. (USN)

Commander - The officer rank between Captain and Lieutenant Commander (USN).

Company - (USMC, US Army) Consists of 130 to 150 soldiers or Marines. Normally commanded by captains and consisting of two or more platoons, usually of the same type, a headquarters unit and some logistical capabilities. Companies are the basic elements of all battalions.

Compensation - The process of transferring ballast, in the form of water, between the variable tanks, and between the variable tanks and sea, to effect the desired trim. 

ComSubDiv - Commander Submarine Division (USN)

ComSubPac - Commander Submarine Force, Pacific (USN)

ComSubRon - Commander Submarine Squadron (USN)

ComSubSoWesPac - Commander Submarine Force, Southwest Pacific (USN)

Collision Bulkhead - The foremost transverse watertight bulkhead in a ship that extends from the bottom of the hold to the main deck.

Condenser - Device for converting exhaust steam from engines into water for re-use.

Conn - The authority directing the steersman, or the act of directing and thus maneuvering the ship. 

Conning Tower - The small, heavily armored horizontal hull directly above the control room and below the bridge. Houses the normal steering stand, torpedo data computer (TDC), firing panel, surface search radar, periscopes, sound receivers (except sonic JP), fathometer, navigational plot, and receivers from the target bearing transmitters (TBT); in essence. the heart of both the ship and the torpedo fire control.

Contact Pistol - Torpedo detonator that explodes upon striking a solid object; also called a contact fuse.

Control Room - The midship compartment containing all diving controls, the ship's gyrocompass and its auxiliary, the air search radar, an auxiliary steering stand, the interior communications switchboard and the radio room.

Convoy - A precise assembly of merchant ships organized in columns and escorted by warships.

Corps - (USMC, US Army) The corps is the largest tactical unit. The Corps is responsible for translating strategic objectives into tactical orders. It synchronizes tactical operations including maneuvering, the firing of organic artillery, naval firing, supporting tactical air operations, and actions of their combat support, bringing together these operations on the battlefield. Each corps will have between two and five divisions, depending on the mission.

Corvette - A highly maneuverable armed escort ship, smaller then a destroyer.

Countermeasure - A device, tactic, or material designed to reduce the effectiveness of an enemy attack.

Course - Direction steered by a ship.

CPO - Chief Petty Officer USN)

Crash Dive - USN term for an emergency dive by a submarine.

CSF - Caribbean Sea Frontier (USN)

Cutie - Passive homing torpedo

CV - Aircraft Carrier (USN)

CVE - Escort Aircraft Carrier (USN)

CVL - Light Aircraft Carrier (USN)

Cypern - A type of radar detector.



D-Day - Day on which an operation is to commence and/or on which troops will depart (Day of Departure).

DD - US Navy designation for Destroyer

DE - Destroyer escort (USN)

Damage Control - Measures necessary to keep a ship afloat, fighting and in operational condition.

Davy Jones Locker - The bottom of the sea.

Day's duty - Tour of duty on shipboard lasting 24 hours.

Dead ahead - Directly ahead of the ship's bow; bearing 000° relative.

Deadweight tonnage - The difference between a ship's light and loaded displacement.

Deck Gang - Men of the ship's gunnery crew; all deckhands.

Deckhouse - An enclosed structure raised above the weather deck of a vessel.

Degaussing Gear - Electrical gear which sets up neutralizing magnetic fields to protect the ship from magnetic action mines or torpedoes. Pronounced de-gow'sing.

Depth Charge - Explosive charge used against submarines.

DesDiv - Destroyer Division (USN)

DesRon - Destroyer Squadron (USN)

Displacement - The weight of a boat or ship, as measured by the amount of water displaced when placing the vessel in water.

Disposition - An ordered arrangement of two or more formations proceeding together.

Distance to Track - The distance in yards to the target track, measured along a line perpendicular to the target track.

DivCom - Division Commander (USN)

Diving Trim - The condition of a submarine when it is so compensated (see compensation) that completing the flooding of the main ballast, safety, and bow buoyancy tanks will cause the vessel to submerge with neutral buoyancy and zero fore-and-aft trim.

Division - In an organization of ship groups: The unit between sections and squadrons; in shipboard operations: a number of men and officers grouped together for command purposes.

Division - (USMC, US Army) Divisions perform major tactical operations for the corps and can conduct sustained battles and engagements. One division is made up of at least three brigades with between 10,000 and 20,000 soldiers. Divisions are normally commanded by major generals. Types of divisions include light infantry, armored and mechanized infantry, airborne and air assault.

Doc - Nickname for personnel with a medical rank or rating (Doctor, Pharmacist Mate, Corpsman, Medic)

Dock trials - Four to six hour trial of main engines while the ship is moored alongside a pier.

Dogs - The pawls securing a watertight door or hatch.

Dog Watch - Normally the 1600 to 1800 and 1800 to 2000 watches, although any four hour watch may be halved or "dogged".

DR - Dead Reckoning position, obtained by using the ships course, speed and elapsed time.

DRI - Dead Reckoning Indicator; receives input from the Bendix Log and gyrocompass, and has dials indicating longitude and latitude.

Draft - The ship's vertical extension below the waterline at various points along the entire length measured in feet and inches. Traditionally measured at the stern, bow, and amidships.

Dräger Tauchretter - (Kriegsmarine) An underwater escape apparatus for U-Boat crewmen.



ECM- (Electric Coding Machine) Standard submarine coding - decoding device. When operating in shallow coastal waters the ECM was sometimes left behind to prevent its falling into enemy hands should the sub become sunk and salvaged; usually a simple strip cipher device was substituted for the ECM.

Echo Sounder - Fathometer; device for measuring the depth of water by sending out vibrations which bounce back from the bottom. It measures time taken for the echo to return, and from that the distance is calculated.

Eel - (Kriegsmarine) U-Boat nickname for a torpedo.

Encryption - Enciphered or coded message.

End Around - Submerged and surfaced maneuver to pass an enemy convoy and gain position ahead.

Engine Air Induction Valve- Large mushroom shaped valve to provide air to the diesels.

Engine Order Telegraph - Signaling gear for transmitting speed and direction from the bridge to the engine room.

Enigma - (Kriegsmarine) The Schussel M cipher machine also used in reference to the machine's encrypted message.

Escort - A ship or aircraft used to protect a merchant ship, main body, or convoy.

Escort Carrier - (CVE) Small aircraft carrier, usually built of a merchant ship hull, designed for anti submarine planes. (USN)

Ensign - Officer rank between Lieutenant (jg) and Chief Warrant Officer. (USN)

ESF - Eastern Sea Frontier (USN)

Expansion tank - Connected between the head box and the compensating water main, admits sea pressure to the fuel oil tanks. It receives any overflow from the fuel tanks resulting either from overfilling the fuel system or from temperature expansion. The bilges are pumped into this tank to prevent leaving an oil slick or polluting a harbor. 

Eye Port - A small, thick glass window in watertight doors and also in the conning tower. 



F-21 - The US Navy Atlantic Section, Intelligence Center, first called OP-20-G at Main Navy; an exact clone of the OIC submarine Tracking Room of the British Admiralty, it began operations in spring 1942.

FAT - (Kriegsmarine) Federapparat torpedo - An anti convoy torpedo employed by U-Boats that travelled in a straight line  for a predetermine distance then zigzagged.

Fahnrich zur see - (Kriegsmarine) Midshipman

Fan - A torpedo spread.

Fantail - Term used to identify the stern deck area of a ship.

Fathom - Six feet or 1.829 meters

Fathometer - (See Echo Sounder)

FdU - ( Kriegsmarine ) Führer der Unterseeboote - Flag Officer for German submarines.

Fido - The "mine" MK24 torpedo

Field Strip - To disassemble without further breakdown the major groups of a piece of ordnance for routine or operating cleaning and oiling; as opposed to detailed stripping which may be done only by authorized technicians.

Final Trim - the running trim obtained after submerging, in which the fore-and aft and over-all weights have been so adjusted that the boat maintains the desired depth, on an even keel, at slow speed, with minimum use of the diving planes.

Fire Control - The mechanics of directing torpedoes or gunfire.

Fireman - Engine room crewman (USN)

Fish - U.S. submariner's nickname for a torpedo.

5ND - Fifth Naval District (USN)

Five by Five - Loud and clear (based on a system of indicating a radio's signal strength on a one to five scale).

500 Tonner - Type VII U-Boat

Fix - An accurate ship's position determined by obtaining star sights or bearings of known landmarks.

Flag Officer - An officer of the rank of Captain or above; so called because he is entitled to fly his personal flag which, by stars, indicates his rank.

Flak - Anti aircraft gun

Flank - Used in ship control language to indicate maximum speed ahead. also means aft starboard or aft port.

Flat - Description or state of a  battery which has been discharged.

Fleet Type Submarine - Attack submarine used during WWII. Approx 250 were built between 1940 and 1945.

Flood Down - Fill tanks until the decks are awash.

Flood Valves - Large Kingston valves located in the bottoms of the ballast tanks to admit water; these valves were removed for wartime patrolling.

Flooding - Filling a tank through flood ports, open flood valves, or other sea connections.

Flotilla - Small fleet of small vessels.

Flotsam - General term for articles which will float when jettisoned. Floating debris left on the surface by a sunken ship.

Flugboat - German for flying boat aircraft.

FM Sonar - Sonar device used by US submarines to detect mines.

Foc'sle - Vernacular for forecastle

Foo Foo - Anything with a pleasant aroma noticeable after several weeks on patrol.

Foo Foo Dust - Talcum powder

Forecastle - A forward upper deck extending to the bow.

Formation - An ordered arrangement of two or more ships or units proceeding together.

Forward - Toward the bow; opposite of aft.

Forward Trim - Variable ballast tank used to adjust the submarine's weight and tilting movement.

Fox Schedule - (Fox Sked) Radio broadcast schedule of messages for U.S. submarines.

Foxer - British noisemaker towed behind ships to fool German acoustic torpedoes.

Fregattenkapitän - (Kriegsmarine) Captain - junior grade

Frontboot - (Kriegsmarine) U-Boat at sea that has entered an operational area. 

Front Porch - Nickname for the 20 mm gun platform just forward of the bridge cowl on U.S. submarines.

FRUMEL - Fleet Radio Unit Melbourne (USN)

FRUPAC - Fleet Radio Unit Pacific (USN)

Fuel ballast tanks - Designed to be utilized as fuel oil tanks for increased operating range. When empty, they may be converted to main ballast tanks, providing additional freeboard and thereby increasing surface speed. (USN)

Full Speed - A prescribed speed that is greater then standard but less then flank.

Funk Telegraphie - (Kriegsmarine) FT - German reference to a wireless telegraphy radio transmission/reception.

Funker - (Kriegsmarine) Navy radioman

Funnel - A ship's smokestack.



G7a - German torpedo propelled by a compressed air system.

G7e - German battery driven torpedo.

Gaining Bearing - Catching up or drawing ahead when pursuing a ship.

Galley - A ship's kitchen.

Ganomie - A sea going Gremlin

Gangway - Any ladder or stairway providing ship to dock or ship to boat access.

Gas Boat - Gasoline driven submarines of the era before diesel engines.

General Quarters - Battle stations for all hands.

Going Hot - Torpedoes properly directed toward a target and as a matter of course, hitting.

GNAT - Name applied to the German T5 acoustic torpedo by the Allies.

GQ - General Quarters

Gradient - A layer, where the temperature of the sea water, and to a lesser degree its density, changes abruptly, thus sending sound waves of echo-ranging clear of a submarine below the layer.

Great Circle - Shortest route, following the arc of the earths surface.

Grossadmiral - (Kriegsmarine) Grand Admiral, corresponding to Fleet Admiral (USN).

Gross Ton - Measure of a ship's size based on volume: The internal volume of a ship (except passenger vessels) converted to tonnage based on one ton to 100 cubic feet.

GRT - Gross Register Tonnage; the total displacement of a ship.

Guide - In general, the ship on which other ships take station when forming, or keep station when formed up.

Gyro Angle - The angle between the fore-and-aft axis of your own sub and final track of the torpedo, measured clockwise from the bow of your boat; the angle set into each torpedo's gyro so that its steering mechanism will bring it to its proper course and hit the point of aim.

Gyrocompass - Compass used to determine true directions by means of gyroscopes.

Gyrocompass repeaters - Compass cards electrically connected to the gyrocompass and repeating the same readings.

Gyropilot - Automatic steering device connected to the repeater of a gyrocompass; designed to hold a ship on its course without a helmsman. 



H-Hour - Time at which an operation is to commence

Hard Dive - Dive at maximum down angle

Hangfire - Gun charge that does not fire immediately upon pulling the trigger, but some time later.

Hatch - An opening in a deck.

HE - (Hydrophone effect) Underwater sound such as propeller cavitation by a surface ship or the path of a torpedo, detected by hydrophone and shown on instruments having a certain bearing or range.

Head - A compartment on the ship containing toilet facilities. Also the ship's stem.

Heel - to list over.

Hedgehog - A type of depth charge employed against U-Boats which were thrown ahead of the ASW ship. These devices were designed to explode on contact.

Hellsbells - name given to sound made by FM sonar.

Hellcats - Nickname for the group of US submarines equipped with FM sonar that conducted mine detection missions and/or penetrated the Sea of Japan (USN)

Hellpot - US nickname for Japanese mine

Helm - The mechanism for steering a ship; wheel or tiller.

HF/DF - (Huff Duff) High Frequency Direction Finder which allowed for the triangulation of the source of radio transmissions.

Higgins Boat - An amphibious landing craft (USN)

HMS - His/Her Majesty's Ship

HMAS - His/Hers Majesty's Australian Ship

Hold - Space below decks for storage of ballast, cargo etc.

Hull Down - Description of a ship beyond the horizon with only its masts or superstructure visible.

Hunter - Killer - A coordinated, aggresive anti-submarine operation by surface ships and/or air units to hunt out and destroy submarines.

Hydra - Cipher used by U-Boats in establishing the daily setting of the Enigma/Schlussel M cipher machine.

Hydrophone - Underwater sound detection device.

Hydroplanes - (see bow planes)

Hypo - US cryptanalysis unit (Honolulu, Hawaii) 



I-Boat - Class of 2,100-ton displacement Japanese submarine.

IC - Interior Communications - Telephone or communications inside of a ship. 

IC Switchboard - Interior Communications switchboard. Handles AC electricity for the gyrocompasses, TDC, interior communications as well as other uses.

ICOPA - Intelligence Center Pacific Ocean Area (US)

IJN - Imperial Japanese Navy



JAAF - Japanese Army Air force

Jam Air - To compress air

JANAC - Joint Army Navy Assessment Committee

Jetsam - Goods which sink when thrown overboard. Opposite of flotsam.

Jettison - The throw goods overboard.

JICPOA - Joint Intelligence Center Pacific Ocean Area

JK - (JK-QC)A dual head, passive/active sound device for supersonic frequencies (too high for the unaided ear).

JNAF - Japanese Naval Air Force

Joe - Coffee

JP - Passive, fixed head sound gear installed in mid 1944; An amplified sonic receiver.

Jumping Wire - Heavy cable with a cutting edge, stretched from bow to stern over the submarine's conning tower, to cut or deflect underwater obstacles like nets.



Kaleu, Kaleunt - (Kriegsmarine) Diminutive forms of the naval rank Kapitänleutnant.

Kapitänleutnant - (Kriegsmarine) Lieutenant Commander

Keel - Main longitudinal structure of the ship, located at the extreme bottom.

Keelhaul - To reprimand severely.

KIA - Killed in Action

Kingston - A valve from the bottom of the ballast tank to the sea.

Kiroshio - The Japanese current

Knot - A ship's speed measured as one nautical mile per hour.

Knuckle - A high speed turning maneuver which can return a solid sonar echo

Konteradmiral - (Kriegsmarine) Rear Admiral

Korvettenkapitän - (Kriegsmarine) Commander

Kriegsmarine - (KM) The German Navy 1935 -1945



Ladder Chancre - Shin bruises caused by the collision with ladders and combings. A common ailment.

Lash Up - Any kind of arrangement or set-up. "That was a bum lash up."

LCC - Landing Craft Command Ship (USN)

LCI - Landing Craft Infantry: capable of carrying 200 infantrymen

LCM - Landing Craft Mechanized (USN)

LCT - Landing craft Tank (USN)

LCVP - Landing Craft Vehicles and Personnel (USN)

LCVR - Landing Craft Vehicles Ramped (USN)

LHA - Amphibious Assault Ship (USN)

LST - Landing Ship Tank (USN)

Lee - Direction away from the wind. 

Lee Helmsman - Assistant or relief helmsman.

Leeward - In the direction that the wind is going or downwind side of an object.

Leutnant zur see - (Kriegsmarine) Lieutenant Junior Grade

Lieutenant - The officer rank between Lieutenant Commander and Lieutenant Junior Grade (USN).

Lieutenant Commander - The officer rank between Commander and Lieutenant (USN)

Lieutenant Junior Grade (jg) - the officer rank between Lieutenant and Ensign. (USN)

Limber Holes - Scalloped opening where the superstructure meets joins the ballast tanks or pressure hull.

Line Officer - An officer who is eligible for command at sea. 

List - Transverse inclination of a vessel.

Logbook - A ledger used to record important daily data and ship's occurrences and activities.

Losing Bearing - Dropping behind when pursuing a ship.

Lung - See Momsen lung



MAA - Master at Arms - Naval designation for the person responsible for discipline and housekeeping in crew areas.

Magazine - Compartment used for the stowage of ammunition and explosives.

Main Body - The principle ships of a formation (other then a convoy) that is being escorted by warships.

Main Ballast Tanks - Tanks that are provided primarily to furnish buoyancy when the vessel is in surface condition and that are habitually carried completely filled when the vessel is submerged, except tanks whose main volume is above the surface waterline. (USN)

Main Deck - Uppermost complete deck of the ship. Areas below this are watertight.

Main Navy - US Navy Department main headquarters building at 7th St. and Constitution Ave. in Washington, DC.

Main vents - Valves operated hydraulically, or manually, for venting the main ballast tanks when flooding. They are located in the top of the risers of the main ballast tanks. (USN) 

Maneuver - A change of speed, course, formation or any combination of these to adjust position or take a new position.

Mark - Call used in comparing watches, bearings or compass readings. 

Mark 18 - A series of electric powered, wakeless torpedoes with a speed of 27 knots and a range of 4,000 yards. (USN)

Mark 14 - A series of two speed, steam powered torpedoes running at 46 knots with a range of 4,500 yards in high power or 31.5 knots and a range of 9,000 yards in low power. (USN)

Mark 23 - A series of two speed, steam powered torpedoes similar to the MK 14. (USN)

Maru - A suffix to the names of most Japanese merchant ships; hence in submarine language any Japanese ship except a warship.

Maximum Speed - The highest speed at which a ship is capable of proceeding when using full power.

Mess - To eat; a group of men eating together.

Mess Deck - Location of the crew's eating area.

Messenger - An enlisted man who runs errands for the OOD. (USN)

Meter - 39.37 inches

MIA - Missing in Action

Midshipman - A student officer.

Minnie the Mermaid - A much discussed character who turns out to be a submerged mural in the diving tower at the New London Submarine School.

Misfire - A powder charge that fails to fire when the trigger is pulled.

Metox - A type of German radar detector.

Milch Cow - Nickname for a type of U-Boat used for re-supply and re-fueling other U-Boats.

MOMP - Mid Ocean Meeting Point south of Iceland where US and British naval escorts exchanged responsibility for guarding Atlantic convoys . Also called "chopline" (change of operational control).

Momsen Lung - A breathing apparatus to permit an individual to breathe normally while escaping from a sunken submarine; also serves as a gas mask in the submarine and as a life preserver on the surface. (USN)

MOT - Middle of Target

Mother Ships - Ordinary ships (usually submarines) that carried "midget" subs (AKA SPS - Special Purpose Submarines) or special forces to sites close to their attack objective.

Muster - To assemble the crew; roll call.



NAS - Naval Air Station (USN)

Nautical Mile - 1.1516 statute miles (6,080.2 feet).

NCO - Non Commissioned Officer (USN)

Negat - US cryptanalysis unit (Navy HQ, Washington, DC)

Negative Buoyancy - A condition attained when the submarine weighs more then the water it displaces, thus causing it to submerge.

Negative Tank - Floodable tank used to impart negative buoyancy to a submarine to make it dive rapidly. (USN)

Nest - Two or more vessels moored alongside one another.

Net - A barrier of steel mesh used to protect harbors and anchorages from submarines, torpedoes, or floating mines.

Neutral Buoyancy - A condition attained when the submarine weight equals the weight of the water it displaces, thus requiring small inputs from the diving planes to maintain trim.

NGS - Naval General Staff (IJN)

Night Orders - The CO's written orders to the OOD while the ship is underway at night including proper speed and course and what to do in the event of an emergency or enemy contact.

NOB - Naval Operating Base (USN)

Normal Approach Course - An approach course perpendicular to the bearing of the target ship.

Normal Course - An approach course perpendicular to the track of the target ship.

Normal Speed - The speed at which ships proceed if a signaled speed is not ordered.




Ocean Going Bellhop - Slang nickname for a US Marine.

On Station - Term to denote the presence of a ship at its assigned location.

ONI - Office of Naval Intelligence (USN)

ObdM - (Kriegsmarine) Oberbefehlshaber der Marine - Supreme Commander in Chief of the German Navy.

Oberfänrich zur see - (Kriegsmarine) Ensign

Oberleutnant zur see - (Kriegsmarine) Lieutenant Senior Grade

One Bell - A single order to maneuvering.

1MC - The submarine announcing system; includes the collision, diving, and general alarms

ONI-208J - Identification manual used by U.S. submarines and aircraft to assist in classifying Japanese merchant ships.

OIC - Officer in Charge (USN)

Oiler - A tanker; a vessel especially designed to carry fuel.

Oiling - Taking fuel on board.

Oil King - A petty officer in charge of fuel oil storage.

Oil Skins - Waterproof clothing.

Old Man - A seaman's term for the captain of the ship or other naval activity.

On the Coral - On the bottom.

OOD - Officer of the Deck (USN). The officer on watch in charge of the ship.

OpNav - Office of Chief of Naval Operations (USN)

Operation Order - (OpOrd) Secret instructions and restrictions governing a submarine's war patrol. (USN)

Operational Speed - The highest speed at which a ship is required to proceed during a particular operation or during a stated period.

Op-20-G - Communications Security Section (USN)

OSS - Office of Strategic Services (US)

OTC - Officer in Tactical Command (USN): The senior line officer present, or the officer to whom tactical command has been delegated.

Out of Trim - To carry a list or to be down by the head or stern.

Outer Doors - Streamlined, moveable shutter-like doors covers over the torpedo tubes.

Overhead - Nautical term for the ceiling of an area.

Own Course - The angle between the North-South line and the fore-and-aft axis of your own boat, measured clockwise from North to your own boat's bow.



PC - Patrol Craft of about half the length of a Destroyer Escort. (USN)

PCO - Prospective Commanding Officer making a refresher patrol prior to taking command of his own submarine. (USN)

PBY - Patrol Bomber aircraft (USN)

Passageway - nautical term for a corridor or aisle on board ships.

Pelorus - A navigational device for taking bearings; consisting of a moveable ring, graduated like a compass card, and a pair of sighting vanes.

Periscope - An extendable, tubelike optical instrument containing an arrangement of prisms, mirrors and lenses that permitted a submarine to view the surface sea from a submerged position or to observe at a level above the eye.

Periscope Depth - The submerged depth at which the periscope extends two to three feet out of the water.

Periscope Shears - Upright supports around the periscopes where they protrude above the conning tower; Lookouts are stationed on horizontal platforms mounted on the shears.

PG - Patrol Gunboat (USN)

Picket Boat - A very fast, sturdy and seaworthy US Coast Guard craft, used primarily for law enforcement

Pickle - U.S. submariner's nickname for a torpedo.

Pigboat -  Nickname for an old type of submarine especially an S Class, so called because of its appearance next to a tender. The term equally fitted the living conditions aboard the boat. (USN)

Pipe Down - Instructions passed over the general announcing system (1MC) to commence an activity. 

Pit Log - Pitometer Log; the scientific name for the speed log manufactured by Bendix.

Pitch - The vertical rise and fall of a vessel's bow or stern caused by a head sea or a following sea.

Platoon - A platoon is four squads - generally three rifle squads and one weapons squad, normally armed with machine guns and anti-tank weapons. Lieutenants lead most platoons, and the second-in-command is generally a sergeant first class.

Point - A point of the compass, accurately 11¼°, employed by lookouts to report the direction of sightings, with each lookout's quadrant divided into eight points.

Pointer - The member of a gun crew who controls the vertical elevation of the gun when it is being aimed. (USN)

Poppet Valve - Valve to vent residual torpedo firing impulse air back into the boat to reduce telltale bubbles on the surface. (USN)

Port - Nautical term indicating the left side or in the direction toward the left.

Positive Buoyancy - Condition a submarine is in when its submerged displacement weighs less then than water it displaces, thus causing it to rise to the surface.

POW - Prisoner of War

PPI - Plan Position Indicator of the surface search radar; on which the image appears as viewed from above with the submarine at its center.

Pressure Hull - The submarines inner hull and conning tower; built to withstand the sea pressure at a stipulated test depth plus a generous safety factor.

Pull the Plug - To submerge



QC - The echo ranging portion of a sound head.

Q Ship - A decoy merchant vessel with flotation cargo and hidden deck armament designed to lure a surfaced submarine to close in destruction.

Quack - A Pharmacist's Mate, also called "Doc'

Quarter - The arc of 45 degrees to either side horizontally from the stern of a vessel.

Quick dive - The rapid submerging a submarine while running on main engines.



RADAR - (Radio Detection and Ranging) the principle and method whereby objects are located by radio waves; a radio wave is transmitted, reflected by an object and illuminated on an oscilloscope or cathode ray screen.

Radar Picket - A ship stationed a distance from the main force for the purpose of picking up by radar the approach of the enemy.

RAF - Royal Air Force (British)

RAN - Royal Australian Navy

Range - The distance in yards from a ship to a target. A navigational range consists of two markers, some distance apart, located on a known line of true bearing.

Rate - Grade of official standing of enlisted men. (USN)

Rating - Name given to an occupation which requires basically related aptitudes, training, experience, knowledge and skills.

Rank - Grade of official standing for commissioned and warrant officers.

RDF - Radio Direction finder (see HF/DF) 

Rear Admiral - the officer rank between Vive Admiral and Captain.

Reduction Gears - A gear train used to reduce the input speed from the main propulsion motors to a lower output speed in the ship's propeller shafts.

Relative Bearing - Bearing in degrees measured clockwise from own ship's bow. The bow of the ship is taken as 000° and an imaginary circle is drawn clockwise around the ship; objects are the reported as being along a line of bearing through any degree division of the circle.

Ride the Vents - A surface condition in which the main ballast tanks are prevented from completely flooding by the closed main vents which prevent the escape of air. (USN)

Rigged for dive -  A state of readiness in which procedures for compensating the vessel and preparing the hull openings and machinery so that the vessel can be quickly and safely submerged and controlled by flooding the main ballast tanks, using the diving planes, and operating on battery-powered main motors has been achieved.  (USN)

Ring the Bell - To hit a target or be hit.

Roll - The side to side movement of a ship at sea.

RN - Royal Navy (British)

RNR - Royal Naval Reserve

RO Boat - A 900-ton displacement Japanese submarine.

Running dive - The submerging of a submarine while running on battery power. (USN)


Safety - A special ballast tank with the strength of the pressure hull; blown and sealed off in an emergency to compensate for flooding within the pressure hull. (USN)

SC - 110', wooden hulled Submarine chaser (USN)

Screw - The propeller of a ship.

Scuttle - The act of deliberately sinking a vessel.

Scuttlebutt - Nautical term for water fountain. Also refers to rumors and gossip, said to originate around the water barrel.

SD - Non directional air search radar. (USN)

Sea Bag - Large canvas bag used for stowing gear and clothing

Sea Frontier Forces - Forces of escort and patrol craft, organized principally for combating the submarine menace in coastal sea areas.

Sea Return - (also Land Return) RADAR interference caused by the return echoes from sea or land. Sometimes called "grass".

Sea State - State of the sea regarding wave action and height of swells.

Section - A unit of a division.

700 Tonner - Type IX U-Boat

Screen - An arrangement of ships and or ASW aircraft whose function it is to protect the main body.

Seabees - Nickname for US Navy Construction Battalions (CBs)

Secure for Sea - Extra prescribed lashing on all moveable objects.

Semaphore - A code indicated by the position of the arms; hand flags are use to improve readability.

Set the Watch - The order to station the first watch.

Sewer Pipe - Nickname for a submarine (USN)

Sewer Pipe Sailor - Nickname for a submariner (USN)

Shakedown - Cruise of a newly commissioned or overhauled ship to test and adjust all machinery and equipment and to train the crew as a working unit.

Shellback - A man who has crossed the equator and been initiated. (USN)

Ship - A general term for large ocean going craft or vessels.

Side lobe - False image appearing on a radar screen to the right and left of a contact.

Signaled Course - The prescribed direction of travel of a ship or tactical organization.

Signaled Speed - The speed at which a formation has been ordered to proceed.

Sitting Pigeon - An unarmed, unescorted enemy vessel proceeding slowly.

SJ - Surface search radar; shows range and bearing to contact. (USN)

Skeg - A continuation of the keel aft to protect the propeller.

Skipper - The captain of any ship. Also to act as the captain of a ship.

Sonar - (Sound Navigation and Ranging) A device for locating objects (esp. submarines) underwater by emitting vibrations similar to sound and measuring the time taken for those vibrations to bounce back from anything in their path. Equivalent to British ASDIC.

SOP - Senior Officer Present (USN)

SOPA - Senior Officer Present Afloat (USN)

SoPac - South Pacific Command (USN)

SoWesPac - South West Pacific Command (USN)

Sound - The man who works the sound devices. Similar to "Chips" or "Sparks".

Snorkel - A tube through which a diesel submarine breathes while submerged.

Sparks - Nickname for the ship's radio man

Spitkit - A small. ramshackle vessel.

Splinter Camouflage - A paint scheme characterized by long, thin sharp edged bands of various colors that obfuscate the form of a warship at sea.

Spread - A number of torpedoes fired at the same target but at different angles.

Squad - (USMC, US Army) A small military unit consisting of 10 to 11 soldiers or Marines.

SS - Submarine (USN)

ST - Radar periscope (USN)

Stadimeter - Periscope range finder; target's height or length must be known to determine range or angle on the bow. respectively. (USN)

Standard Rudder - The amount of rudder angle required to cause a ship to make a turn within a certain standard tactical diameter.

Starboard - Nautical term indicating the right side or in the direction toward the right.

Station - The prescribed position of the ship in relation to the guide.

Stationary dive - The submerging of a submarine without headway or sternway. 

Steerageway - Nautical term for minimum forward speed that will provide safe steering capability or directional control.

Stem - The extreme forward line of the bow.

Stern - The rearmost area of the ship. Opposite the bow.

Stern Planes - The pair of horizontal rudders at the submarines stern, used to control the angle of the boat and when used in coordination with the bow planes, to maintain or change depth.

String - Similar to a fan or a spread, but referring to a number of depth charges dropped in a single run of the patrolling surface ship at regular intervals.

Submerged condition - Designates a condition of a submarine in which all fixed portions of the vessel are completely submerged and the variable ballast is so adjusted that the submarine has approximately neutral buoyancy and zero fore-and-aft trim. 

SubRon - Submarine Squadron (USN)

Surface condition - A condition when the submarine has sufficient positive buoyancy to permit running on her main engines.

Superstructure - Structure built above the ship's hull.



T5 - German acoustic torpedo, called GNAT by the allies

Target Course - The angle between the North-South line and the fore-and-aft axis of the target, measured clockwise from North to the target's bow.

Task Force - A temporary grouping of units under one commander; formed for the purpose of carrying out a specific mission or operation.

TBS - Talk Between Ships (USN)

TBT - Target Bearing Transmitter, one forward and one aft of the bridge; receives binoculars for transmission of bearings to the conning tower. (USN)

TDC - Torpedo Data Computer. Keeps the range to the target current and displays the respective aspects of target and own ship; its angle-solver section computes the proper gyro angle and continuously sets the angle into all torpedoes readied for firing. (USN)

Telephone Talker - A man who handles the sound powered phone during drills. (USN)

Tender - A auxiliary vessel that supplies and repairs ships or aircraft.

Tin Can - Nickname for a Destroyer (USN)

Tonnage War - The attempt by German U-Boats to destroy more ships then the Allies could build.

Topside - Exposed or semi-exposed, non watertight areas of the ship. The main deck.

Torpedo Gyro - The heart of the steering mechanism of a torpedo.

Torpedo Run - The distance in yards which the torpedo travels from the tube to the target.

Torpex - The explosive in torpedo warheads; a combination of Cyclonite, TNT and metal flakes.

Track - The path of a vessel.

Track Angle - The angle between the fore-and-aft axis of the target and the torpedo track, measured from the target bow to starboard or port.

Transfer - The distance gained at right angles when turning.

Trim - The balancing of a submarine's weight and equilibrium underwater.

Trim Down - Reduce buoyancy until the boat is running virtually awash.

Trim Pump - A dual piston pump for shifting ballast and for pumping to sea.

Trim Tanks - The variable ballast tanks located nearest the bow and stern of the boat and are used to provide fore-and-aft compensation.

True Bearing - Gyrocompass bearing, or bearings in degrees measured clockwise from earth's true north.

True Target Bearing - The angle between the North-South line and the LOS, measured clockwise from the North.



U-Boat - A German submarine, generally larger then 200 tons.

Ultra - A priority message with information derived from a decoded Japanese transmission.

Unit - A single ship or aircraft, or a small number of ships and/or aircraft operating as an entity. Thus, 2 submarines (units) form a section, 2 sections form a division, 2 divisions form a squadron.

Ubootwaffe - The German submarine (U-Boat) fleet

Unterseeboot - "Submarine" in German, abbreviated as U-Boat in English.

USCG - United States Coast Guard

USN - United States Navy

USNR - United States Navy Reserve

USS - United States Ship



Variable Ballast Tanks -  Tanks that are not habitually carried completely filled when submerged and whose contents may be varied to provide weight compensation. Variable ballast tanks are constructed to withstand full sea pressure. (USN)

Vessel Ton - 100 cubic feet

Vice Admiral - The officer rank between Admiral and Rear Admiral.

VMF - Designation for USMC Fighter Squadron


Wake - Formation of water turbulence and air bubbles left by a moving ship.

Wardroom - The shipboard officers' mess and lounge. Also refers to the full complement of officers aboard a ship.

Watch - A period of duty, usually four hours in duration.  Watches call for a variety of Navy skills and are of many types: Quarterdeck watch, messenger watch, damage control watch, signal watch, radio watch etc. Standard Navy watches are: First Watch - 2000 to 2400; Midwatch - 0000 to 0400; Morning watch - 0400 to 0800; Forenoon Watch - 0800 to 1200; Afternoon Watch 1200 to 1600; First Dogwatch 1600 to 1800; Second Dogwatch - 1800 to 2000. (USN)

Watch Officer - An officer regularly assigned to duty in charge of a watch or a portion thereof; for example, the OOD, or the engineering officer of the watch.

Watch, Quarter and Station Bill - Posted listing of personnel duty stations for all ship's routine and emergency activities.

Water Slug - Water taken into a torpedo tube after firing, to compensate for the loss of weight of the torpedo.

Way - A ships movement through the water.

Weather Deck - The uppermost deck extending from side to side, in any part of the vessel.

WIA - Wounded In Action

Wintergarten - The open, railed platform on the after part of a U-Boat bridge. Similar to a US submarine's cigarette deck.

Wolfpack - A group of submarines acting as a unit.

WRT Tanks - The WRT, or water round torpedo, tanks are variable ballast tanks, located in the forward and after torpedo rooms, for flooding or draining the torpedo tubes. (USN)




Y Gun - A two barreled anti-submarine gun used to launch depth charges. (USN)

Yard - A spar running athwartships from a mast; Also short for shipyard.

Yardarm - The outboard end of a yard.

Yardarm Blinker - An electric lamp fastened to the yardarm, near its' end; This lamp is operated by a key at a signal station (signal bridge etc) so as to transmit Morse code.

Yawl - A small craft used primarily for planting and collecting submarine mines.


Zeke - A Japanese Zero fighter plane or bomber.

Zero Ward - Where wounded, sick and dying patients were sent when nothing could be done to save them (USN)





WW II US Navy hull abbreviations

WW II US Navy ratings abbreviations, pay grades and ship organization







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